November 8, 2016

expert reaction to vaping and smoking

A research letter published in JAMA has examined the association between e-cigarette use and progression to smoking in a group of adolescents in the US. A Before the Headlines analysis accompanied these comments.

Prof. Paul Aveyard, Professor of Behavioural Medicine at the University of Oxford, said:

“This study shows that teenagers aged 14-16 years who vape are more likely to be smoking and smoking more six months later than similar children who do not vape. The question is why? This study could not tell us if it is something about the young people that vape that predisposes them to smoking or that vaping itself makes smoking more likely. The authors tried to account for other factors that make smoking more likely, but it is never possible to do so completely. We know from analogous studies that people who do one risky behaviour are more likely to be doing another risky behaviour in the future even accounting for a similar set of risk factors. For example, studies of young people show that smoking at baseline predicts drinking at follow-up, while drinking at baseline predicts smoking at follow-up. It makes no sense to say that smoking causes drinking, while saying drinking causes smoking. In the same way, it may be that it is not sensible to conclude that vaping causes smoking. Rather the two are related because young people who are attracted to one are attracted to the other.

“This study is investigating the gateway hypothesis. In practice, it is almost impossible to properly test this hypothesis. Showing that one behaviour precedes another is not enough.

“It’s important to put these results in context. Smoking in young people has fallen in the UK and the US to record lows in the past few years, despite the rise in prevalence of young people experimenting with e-cigarettes. Very few young people who do not smoke cigarettes become regular users of e-cigarettes. In this context, we should not worry unduly about this study’s findings, but it is important to monitor smoking in young people and its relationship with e-cigarette use.”

Prof. John Britton, Director of the UK Centre for Tobacco & Alcohol Studies at the University of Nottingham, said:

“This study indicates that young people who vape are more likely to become smokers. However, this doesn’t tell us whether vaping caused these young people to start smoking, or whether they would have started smoking anyway; or whether vaping prevented some young people who would otherwise have become smokers from progressing to tobacco smoking.

Numerically, the association between vaping and smoking is dominated by young people who were already experimenting with tobacco at baseline; surely we can’t blame vaping for smoking uptake among people who already smoke. If we look only at those young people who had never smoked at baseline, the numbers who progress to smoking are very small: only 26 people (less than 1% of baseline non-smokers) who had vaped in the past month at baseline had smoked in the past month at follow-up.

“Children who live with a parent or sibling who smokes are around twice as likely to become smokers as those who do not. Those children are also far more likely to be exposed to, and have access to, electronic cigarettes than children whose parents or siblings do not use nicotine. For this and other reasons we would therefore expect children who experiment with vaping to be at increased risk of smoking. The key question is whether vaping is increasing smoking uptake, over and above that underlying risk. This study doesn’t answer that question; but it does show that if it does, the proportions of children affected are very small.”

Prof. Peter Hajek, Director of the Tobacco Dependence Research Unit at Queen Mary University of London, said:

“People who smoke are more likely to also try vaping and those who vape more likely to try smoking than people who do not do such things – in the same way that compared to teetotallers, people who drink red wine are more likely to try white wine too. The reassuring news is that in this sample of over 3,000 16-year olds, prevalence of both smoking 3 or more cigarettes in the past months or vaping 3 or more times in the past months were below 5%. The study unfortunately provides no information on daily use which is a marker of a more serious habit, but this was likely much lower.”

‘Association of e-Cigarette Vaping and Progression to Heavier Patterns of Cigarette Smoking’ by Adam Levanthal et al. published in JAMA on Tuesday 8 November.

Declared interests

Prof. Aveyard: I have no financial relationships with any company making products for smoking cessation or e-cigarettes. In one study I lead, Glaxo Smith Kline have donated nicotine patches free to the NHS in support of the study.

Prof. Hajek received researcher funding from and provided consultancy to manufacturers of stop-smoking medications. He has no links with any e-cigarette manufacturers. His research into e-cigarette safety and effects has been funded by NIHR, PHE, UKCTAS and MHRA.